This study will examine aspects of neuronal plasticity in the developing and mature central nervous system (CNS) involved in the functional (metabolic) reorganization of pre-existing neural connections in response to receptor organ damage. Central plasticity is especially relevant to such issues as recovery of cortical function following partial loss of sensory input, the pathogenesis of congenital CNS malformations, skill acquisition, and brain information storage processes in the normal animal. These experiments will extend our knowledge of the means by which to evaluate the effect of treatment on improving functional recovery as well as provide the evidence needed to determine the level of recovery. First, using a labeled analogue of glucose, 2-deoxy-D-(14C) glucose, (2DG method) injected into a naive (unaltered) rat, the normal pattern of metabolic (functional) activity in the afferent pathway between peripheral receptor and cortical representation will be analyzed through quantitative autoradiography following C3 vibrissa stimulation. Second, utilizing the same labeling technique, a separate group of rats will be examined following peripheral receptor organ damage (ablation of all facial vibrissa follicles except C3-spared C3 model). The spared C3 vibrissa will then be stimulated and the 2DG labeling analyzed in order to examine the effect of peripheral sensory denervation on functional reorganization at subcortical levels in the precisely organized rat facial vibrissal-cortical "barrel" system. Third, light microscopic anatomical changes associated with the functional reorganization in the deafferented rat CNS will be examined, aided by the precise metabolic map produced by the autoradiographic 2DG technique. Finally, the relationship between the stage of CNS development and the extent and pattern of subcortical functional reorganization will be studied in the vibrissa-deafferented rat.